Ground trainer for aircraft personnel



J J. LUKACS ET AL GROUND TRAINER FOR AIRCRAFT PERSONNEL JJ. uA/Aas NVU/TOR; R. o. R/PPERE @6. cS-lm' ATTORNEY May 31, i949.

Filed March 1. 1945 May 3l, 1949. J. .1. LuKAcs ET AL GROUNS 'TPAINER FOR AIRCRAFTl PERSONNEL 8 Sheets-Sheet 2 Filed March 1, 1945 wlmi NNN JJ u Acs NVEYTORS/e o. R/PPERE ATTORNEY May 31, 1949. J. J. LUKAcs ET Al.

GROUND TRAINER FOR AIRCRAFT PERSONNEL 8 sheds-sheet s Filed March l; 1945 WR. 6m Sms J. J. UK/165 N VENRS/a 0. R/PPERE A TTQQA/E V May 3l, 1949. J. J. LuKAcs ET AL GROUND TRAINER FOR AIRCRFT PERSONNEL 8 Sheets-Sheet 4 Filed March l, 1945 May 3l, 1949. J. J, LuKAcsv ET AL GROUND TRAINER FOR'AIRGRAT PERSONNEL 8 Sheets-Sheet 5 Filed Marh l, 1945? A T TORNEV May 31, 1949. J. J. I UKAcs ET AL 2,471,966

GROUND TRAINER FOR AIRCRAFT PERSONNEL SOUND Y EFFECTS HRI/J7' HORSEPOWER C/ J. J UKA cs 9 N gms/e. 0. R/PPERE @ma A 7' TORNE V J. J. LUKACS ET AL GROUND TRINER FOR AIRCRAFT PERSONNEL May 3l, 1949.

May 31, 1949. J. J, LUKACS ET AL 2,471,966

GROUND TRAINER RoR AIRCRAFT PERSONNEL Filed March 1,1945 8 Sheets-sheets A TTORNEV Patented May 31, 1949 NHTED STATES OFFICE GROUND TRAINER FOR AERCRAFT PERSONNEL Application March 1, 1945, Serial No. 580,324

14 Claims.

This invention relates to an aircraft trainer in which the operation of controls, similar to those of a standard aircraft, by the pilot, copilot, navigator or flight engineer, causes the operation of instruments on the pilots, navigators and engineers instrument panel and of instruments at the instructors desk to simulate the instrument operations of an actual aircraft in ight whereby an aircraft crew may be given ground training to enable the crew members to coordinate their efforts to insure efficient aircraft operation under actual flying conditions in a regular aircraft.

In the training of aircraft personnel it has been the practice heretofore to give pilots basic training in aircraft of the trainer type and to give ight engineers and navigators ground training with the actual equipment of aircraft. Following such basic training it has been the practice to form crews from such basically trained personnel and to give such crews coordinated training in the iiight of actual aircraft which they will later be assigned to ily in combat duty.

The larger aircraft, particularly multi-engined bomber airplanes are costly to build, to ily and to maintain and the use of such airplanes for extended training purposes with crews Who may have had little actual experience in their operation, introduces a great hazard both to the equipment and to 'the operating personnel during the training period and obviously withdraws such airplanes from their more valuable use in actual combat services.

Since the members of the crew have all had basic training in iiying and in the operation of equipment of airplanes, the actual ilying hours in the type of airplane which they will ultimately be assigned to fly may be materially reduced through the use of a ground trainer designed to simulate all of the ight and operational functions of the type of airplane to which they will later be assigned. After coordinated training in such a ground trainer, the crew training may be completed within a comparatively few hours of flying in an actual airplane.

In the application of R. C. Davis, E. J. Fogarty and R. O. Rippere, Serial No. 542,986, led June 30, 1944, a ground trainer has been disclosed in which an airplane crew may be trained to perform all of the flight and operational functions which would be required to actually y and operate an airplane which the trainer is designed to simulate. In the application of J. J. Lukacs and W. B. Strickler, Serial No. 542,846, iiled June 30, 1944, those portions of the same ground trainer have been disclosed which relate particularly to the training of the pilots and the flight engineer in the performance of all operational functions concerning the equipment of an airplane, as distinguished from flight control functions, which would be required to actually control the equipment of an airplane which the trainer is designed to simulate.

The present invention relates more particularly to an improvement in the circuits disclosed in the Lukacs and Strickler application above referred to, for simulating the engine and propeller operations of an aircraft, and has for its object the provision of means whereby the effects ci the propeller efiiciency upon the thrust horsepower output of the engine-driven propeller is more accurately determined and the provision of means whereby the simulation of the manual and automatic control of the propeller pitch is made more realistic and in aA simpler manner.

These objects have been attained by the provision of a propeller slip ratio motor unit which replaces the former V/ND motor unit and the elimination of the former RPM memory motor unit with the resulting changes in the RPM, propeller pitch, manifold pressure, thrust horsepower and engine Icontrol circuits.

One feature of the invention is the provision of a manifold pressure circuit for each simulated engine which is responsive to the engine control circuit of the corresponding simulated engine, to the RPM circuit corresponding to the same simulated engine, to the altimeter circuit of the trainer, to supercharger blower speed controls at vthe flight engineers station, to throttle controls accessible to the pilots and to the flight engineer and to a control at the instructors desk. The manifold pressure circuitis instrumental in controlling and associated manifold pressure motor control circuit to control other control circuits of the trainer and to control the operation of the manifold pressure indicators on the pilots, iiight engineers and instructors instrument panels.

A further feature of the invention is the provision of an RPM circuit for each simulated engine which is responsive to the control circuit of the corresponding simulated engine, to the manifold pressure circuit corresponding to the same simulated engine, to the true air speed circuit of the trainer, to the propeller pitch circuit corresponding to the same simulated engine and to the throttle controls accessible'to the pilots and flight engineer. The RPM circuit is instrumental in controlling anassociated RPM motor aimee@ control circuit to control other control circuits of the trainer including a tachometer motor control circuit for operating tachometers on the pilots, flight engineers and instructors instrument panels, a sound eects circuit which simulates theexplosionfnoises of :the-aircraft engine and a vibration vsinziulating motor-circuit.

A further feature of the invention is the provision of a propeller pitch circuit for each simulated engine which is responsive to the engine control circuit of the corresponding simulated engine, to the propeller governor and throttle controls accessible to thepil'otsiand to'theight engineer, to the manifold spressurelcircuit corresponding to the same simulatedfenginefand to the true air speed circuit of the Atrainen which propeller pitch circuit is instrumental incontrolling an associated propeller pitch motor control circuit to control the operation of :other control circuits of the trainer.

A'further featurenof-the invention isthe provision of yathrust horse-power circuit common to both simulatedfengines which is responsive tothe brake horse-:powerand'propeller slip ratio circuits relating to both simulated engines and to the enginecontrol-circuitsof both simulated engines, which .thrust horse-.power circuit is instrumental in controlling van associated thrust horse-power motor-control lcircuit to control the operation of other' control circuits of the trainer.

Afurther feature of thednvention is the provision of a propeller slip ratio circuit for each simulated engine whichf-is responsive tothe true air speed circuit of thetrainer and to thepropeller pitch and RPM circuits corresponding to the same 'simulated engine, which .propeller pitch circuit is'instrumental in controlling an associated vpropeller Vslip.ratio motor control circuit to control-'the operation' ofother control circuits of' the trainer.

Other-.features of theiinvention will become apparent 'upon *the .consideration of Vthe following detailed descriptionfof the invention' whenread in connection with the-accompanying drawings in which:

Fig..1 shows:schematically'inthe upper right portion thereofthe motor'and controlrelays of the propeller-slip ratio=motorcontrol circuit for the simulatedright'rengine, in the .upper `left portion thereof `the motorr andfcontrol=relays of the propeller ,slip ratio motor control'. circuit for the simulatedileftiengine,in the lower'right portion thereof the motor` and control-relays of the brake horse-:power:m'otorzcontrol circuit for the simulated right :engine andv ini` .the lower left portion thereof!themotorqandicontrol-relays of the brake horse-power motor controlrcircuit for'the simulated leftf engine;

Fig. 2 shows in tl'ie-upperportion thereof the propeller Yslip ratiocircuitsand in the lower portion thereof the'brake horse-power circuits for both simulatedfengines;

Fig. 3 showsinthe upper portion .thereofthe RPM motor control circuit for the right'engine and in the flower'lportionIthereof 'theimotor and control relays ofthe-"manifold pressure motor control circuits: forfthefrightfengine.

Fig. 4' shows: infthezupperfportion thereof the RPM circuit -and f-in fthe s lower T-lportion thereof the -manifold pressure i circuit. for .the right engine;

Fig. 5--shows fintherupper rightportion thereof the motor:ar1d^control relays ofthe thrust horse-powermotori. control circuit, in the` upper left'portion :thereof-the motortand controlxrelays of the altimeter motor control circuit of th trainer, in the lower right portion thereof the motor and control relays of the propeller pitch motor control circuit for the right engine and in the lower left portion thereof the motor and control relays ofthe trueairspeed motor control circuit of the trainer;

Fig. 6 shows in the upper portion thereof the -thrust horse-power circuit and in the lower portion thereof the propeller pitch circuit for the right -engine Fig. 7 shows in the upper right portion thereof the ,propeller governor, throttle and propeller pitch controls accessible to the pilots and to the flight engineer `and the ignition key accessible to the lpilots, in 'the upper left portion thereof a manifold pressure control and engine disabling key at the instructors desk, in the lower right portion thereof supercharger blower speed and mixture controls and fuel supply control relays at the flight .engineers station, and in :thellower `left portionithereof the motor and controlsrelays of the fuel pressure motor unit for the 4rightengll'le;

Fig. 8 shows -such portions of the controlicircuit for the right engine as are deemedY necessary for any understandingrofA the invention;y and Fig. 9 is a diagram illustrative of'how the several figures ofthe ydrawing should be assembled to completely disclose the invention.

The motor'controlcircuits are in general-associated in pairs. :For example, the two propeller slip ratio motor controlicircuitsschematically illustrated'in the upper portion of Fig. '1 and all of the potentiometersdriven from their driving shafts constitute .azsingle assembly. Each' motor control circuit comprises 'a direct current reversible motor whichythrough a reduction gear box, drives ai main' driving. shaft which, in turn, may drive one or more synchronous transmitters of the so-called ".aut'osyn type for controlling instruments remotely mounted on instrument panels of the trainer or on the instructors desk, may drive potentiometers `or variableauto-transformers ofthe iso-called Variac type'forcontrolling other motor control circuits `of the trainer and drives limit-switches to insure that the driving motor will be'. arrested before the4 sliders :of the potentiometers or variacs :are driven .beyond the ends of 'the windings with which .they :are associated. .This equipment is' mounted on a motor :plate `,as schematically illustrated .innthe Patent No, 2,428,767,.granted October 14, 1947,' to W. P. Albert, R. C. Davis, R. H. Gumley, and W. H. T. Holdes. The relays, condensers, .resistances, control rheostats, testing jacks and 4electronic devices vassociated with the equipment `mounted on theA motor'plate are located on 4an apparatus 'rack'positioned' above 'andf secured to the motortplate. :Several of .these motor plate and' mounting rack: assemblies are mounted one above' the other.l in'apparatus. cabinets.

.Each of theimotor control circuits, folexample .the circuit Vdisclosed in full inthe 'upper :portion of Fig. 3, is disclosed-and ful'lydescribed'-rlnfthe Patent No. 2,428g767 above-referred'to. Alingeneral the :circuit for controlling the'motorflll comprises adual 'triode amplier ltubeilll which receives .asignal 'incoming on conductor l1.00,

'.famplifles' itY and-applies rit `-through the. step-up transformer"l 3ll2v to .the '-.anodes of .the dualidiode rectifier tube1303. :The tube.303 serves asaifull wave rectier to-rectifythe output potential from tube 3D0 .anditoapply .'it;as azpositive .potential 'to the *.grid 'of tgas-lledtubexll. The .output g potential from tube 3D0 is also applied to the control grid of tube 305. Direct current for furnishing grid bias to the control grids of tubes 304 and 385 is supplied from the left secondary winding of power transformer 396 through the dual diode rectiiier tube 391 under the control of the grid biasing control rheostats Sli and Filament heating current for all of the tubes is supplied from the other secondary windings of the power transformer 396. Anode potential is supplied to the anodes of amplier tube Silil from the anode battery B3 and (iO-cycle anode potentials 180 degrees apart in phase are applied to the anodes of tubes 306i and 365. 1Potential of phase ci is applied from the phase ci, l15volt bus bar il5| through the winding of anode relay 342, designated as RV to the anode of tube 305 and potential of phase (,152 is applied from the phase o2, 11S-volt bus bar i l52 to the anode of tube 301i.

The motor 3M is of the direct current reversible type having its stator circuit energized by current from the direct current source B5 from the bus bar ltt-- under the control of reversing relay SIS, designated as RVi which is in turn under the control of anode relay RV associated with the gas-filled tube 305, and Whose rotor winding is energized by positive impulses of current transmitted therethrough by the firing of the gas-lled tube 30d. When the input potential applied to conductor 4M is in phase with the potential of phase el applied to the anode of tube 395 and out of phase with the potential of phase c2 applied to the anode of tube Stil, relays RV and RVi will not operate and motor tiri will be operated in response to the incoming signal in one direction of rotation and when the input potential is out of phase with the potential of phase gbl applied to the anode of tube 3435 and in phase with the potential of phase p2 applied to the anode of tube 3M, relays RV and RVi will operate and motor 314 Will be operated in response to the incoming signal in the reverse direction. The motor terminals are so connected that with relay RVi energized, the sliders of the potentiometers driven by the motor through the reduction gear box Sli and the shaft Sie, are moved toward the No. l terminals of their windings and the motor is stopped by the operation of the cam-operated limit switch Li when the sliders approach the No. l terminals, and with relay RV i unenergized the sliders of the potentiometers are moved toward the No. 3 terminals of their windings and the motor is stopped by the operation of the cam-operated limit switch l L2 when the sliders approach the No. 3 terminals of their associated windings.

The potentiometers and variacs which are driven by a motor control circuit may enter into the control of several other motor control circuits of the trainer. For example, the RPM motor control circuit disclosed in Fig. 3 has a variac RRV, in Fig. 4, in the circuit of a vibrator motor which simulates the vibrations set up by the operation of an engine, a potentiometer (not shown) associated with a tachometer motor control circuit, a potentiometer (not shown) associated With the fuel flow circuit, a potentiometer RRPI associated with the brake horse-power circuit of Fig. 2, a potentiometer RRPZ associated With the propeller slip ratio circuit of Fig. 2,

potentiometers RRP3 and RRP5 associated with the manifold pressure circuit of Fig. 4 and a balancing potentiometer RRPIG associated with itsown control circuit of Fig. 4.

As previously stated, these variacs and poten-` tiometers would all be mounted on the motor plate of the RPM motor unit and conductors would be extended therefrom to the various parts of the trainer where their controls are to be exercised. However, for the purpose of simplifying the disclosure so that all variacs and potentiometers which enter into the control of any one motor control circuit may be shown grouped together adjacent such motor control circuit, the driving shaft of each motor control circuit has been schematically illustrated as geared through unity ratio bevel gears, such as Gill, to a shaft, such as itt, which extends across the several circuits over which the variacs and potentiometers which it drives exercise control.

Since the present invention is primarily concerned with those portions of the apparatus and circuits of the trainer which are applicable to the training of the flight engineer and pilots in the performance of their duties with respect to the operation and control of the main engines cf the aircraft which the trainer simulates, the flight controls, flight instruments and the motor control circuits of the trainer which are responsive to the` iiight controls for simulating night conditions and for simulating the operation of the flight instruments have not been disclosed herein. For a full disclosure of such apparatus and circuits, reference may be had to the application of R. C. Davis, E. J. Fogarty and R. O. Rippere hereinbefore referred to.

Furthermore, some of the circuits appertaining to the simulation of the operation of the main 1 engines, such as the fuel flow, tachometer, cylinder and oil temperature and oil pressure circuits, and most of the apparatus at the flight engineers station and at the instructors desk have been omitted. This apparatus is fully disclosed in the i application of Lulracs and Strickler hereinbefore referred to and on which this application is an improvement.

Since, however, the operation of the main engines of an aircraft is aected by the altitude at which a flight is being conducted and by the true air speed of the flight, the effect of altitude upon the circuits which simulate the operation of the engines is introduced by the potentiometers AF2, APS and APi, the sliders of which are driven from shaft 92 which is in turn driven through the unity ratio bevel gears tti, shaft 528 and the reduction gear box 512i by the motor 522 of the altimeter motor control circuit disclosed schematically in Fig. 5. The effect of the true air speed is introduced by the variac TASVI and potentiometer TASP driven by shaft ttt, in turn driven through the unity ratio bevel gears iiil, shaft 5d@ and the reduction gear cox 5M by the motor of the true air speed motor control circuit disclosed schematically in Fig. 5.

The apparatus employed in carrying out the invention having now been briefly described, the operation of the apparatus for crew training will now be described. Preparatory to simulating the starting of the right engine, the flight engineer operates the carburetor control switch therefor (not shown) to its direct air position, operates the mixture control switch itil therefor to its rich mixture position and operates the supercharger blower speed control switch '55d therefor to its low speed position.

Before simulating the starting of the right main engine the pilot places the propeller governor lli for the propeller driven by that engine in the maximum RPM increase position; pushesignition switch full 'inf; closes the rightland 'lef-.t engine ignition ekeys Y! 102 f and "H13 to the JBQKFH closed positions; Aand operates jthe throttle-1184 f-to its extreme closed positioninWhichdthebrushes of the rheostats 185, 106" and fm1 :operated-thereby are-moved tofthe lowerfC -or closed-terminaisof their associated `windings.

With the ignition ykey -1U2"-operated-to-the BOT-H position, indicating that'bothi'the rig-ht and left vm-agnetos are to-'be-usedinestarting the'zri-ght engine, ground is-removed1from-l1the left contact of such key opening the shunts established over conductor i166 around fthe 'winding `:oT-*the IGL relay 80E)- andground -is Yremoved the right contact of such Akey, Aopening the shunt established over conductor 109faroundftheuwinding. of

the .I'GRrelay Bill. Relay-'80Dnow-operates in 4a circuit lfrom. battery through resistance 1802- to ground through its windingandsrelay BDI operin 'circuitfrom battery:through-:resistance l 8213 `through 'its winding.

'With the rightfpropeller controlwswitoh 'H10 in its upper v or automatic position, uswitch 'LILI i in fits upper or normalposition andrelay- I=21operated by :the v previous operation f of. ftheaight :propeller governor.circuit :breaker i113, ia rcireuit -iis established fromgroundoverthecontacts-nfrelay'l'l I 2, contacts `of :switches '1H and '.'1 Ii,.=over:conductor i lil l.through the Wind-ing' of relayiSM- fito battery. Relayill upon operating releases-relay; .Witlz relay. 885 .released a @circuit .is established from the slider of potentiometer b1 lpfpositionedaiatlthe No. -3 terminal. of itslwn'ding` leystheiniovement ofthe. propeller governor controlL'IILto-i itsMlA'X- 'RPM position. over v:conductor ETI 6, over ithe iupper back-contact of relay k8|l5,fthr.ough resistance to the signalinput conductor .532 `'ofnthepropeller .pitch `motor control :circuit :for the fright engine disclosed .schematically in. PFig;e5. `l'Ihe `Winding -of potentiometer r1 I 5 .is y@energized x over a circuit extending from ground, .'.through resistance 'II'I, through the potentiometervwinding, .through resistancel I3 andover *.-conliuctorlfl I 9 to ethetphaseflpZ busrbar A0412. 'Thisxbusrbardstsupplied with: potentialffromtthe lzevoltialternatin; current sourceikthroughl theftiiansformeri.

' .The mid-point ofthe secondary-.winding off transformer BBS 'being grounded a0-volt ipotentials of phases o I .and 2 are simultaneously .applied to the ybus Abars Doll and ill/4h52. "Iloiseoure the de .sired operating potential across :the .vvin'dingy or potentiometer :l t5, currentfflo-wingsover:conductor i I Sis ,-reduceol; by?thetserieseconnected:resistance l It anch bytheresistancesflI-'l and ilzwhich: to-

gether shunt :the winding .fof :the l potentiometer.

.With the .-maximum .potential oflphase .Mederived f from :the i. propeller 1. governor 1 potentiometer fl I l applied to the :signal 'input conductor i532, this potential .amplified .-byian :amplifier tube (not shown) ,but .corresponding-Ltotube 30.6, is rectied :by vthe `tube .(not shown) but :corresponding t0 tube 3113 and.= is i impressed .upon-the control `grids 10i Atubes :'(not y:shot/vub) 'but-corre spending to tubes. 304 and 30,5..ns-.fafresultgtubes corresponding` to tubes :T3114 and 35=1a1iesboth ,-operated I and `the `IRVI relay c2533 becomes .operated and the. motor 34 iis operated -tofoause :the rotation of shaft '.530 .and :through the; unity fratio :gears i. 62 I fto rotatethe `:shaft 622 fins-.suoni a direction as i to move :fthefsliders of :the z potentiometers RPPI and REBS rtotheiriNo. 1i-terminals representative of :a :reduction in propeller epitch `torreduce fthe fdragnon 4the engine when fstartmg.

When :the sliders. of i-the rpotentiometers RPPI .,andRRBSapproachithe o. r1; terminalsfof .their Windings,;the 'LI limit switchl isoperatedt0iits yalternate position by cam `535 thereby establishv--ing the circuit ofthe LS relay= 535 whichmaylbe traced from ground over the alternate contacts vcillin-lit switch LI, over the leftifront contact of relay 533 to battery through the winding.v of .relay i536. Relay 536 thereupon operates andopens the armature or rotor circuit of motor 534;to

Icause the motor to stop.

'The flight engineer to simulate thestarting of the right engine 'now operates the right engine start key (not shown), to the on position for approximately twelve seconds and then .tothe "inesh position thereby causing the operation of relays including STW relay 333 and a timingztube ultimately resulting in the operation .of lthe STB/ii relay tt! which in turn causes the-,operation o the STM relay Bl. Ilz-being assumed .tha-tithe engine is cold, the nightengineeralso operates the priming key (not shown) ,resulting vinthe.operation of the PRM relay v18H. The manner in which relays S39, Gill and 7,8II are operated is fully discussed in the application of 'Lukacs and Stricliler hereinbefore `referred to.

:Prior to the operation of relay 8m -a circuit is eiective for starting the motor .,354 fof'the :manifold pressure circuit of Fig. .Bextengding from ground through resistance i383, through potentiometer all@ drivenirom the altimeter-motor-controlcircuit (the Winding of which potentiometer is energized over a circuit from `ground through `resistance 3,3 from the @Sol bus bar), overton- `ductor 1336, over theupper backfcontact of fthe FL'relay 8I2, `over the inner upper back contact ofthe STM relay t, over-the lower.back;con

`tact of the ESTl relay l3, conductor @435,and through resistance :56 to the signal input 'conductor 4G? of the manifold pressure motorfeontrol.circuit or Fig. 3. `The potential lapplied to conductor xlt'l'is amplined by an ampliertube r`(not shown) but corresponding to'tube 3mi-,and

is impressed upon the control grids of `motor tcontrol tubes (not shown) but similar tortubes :3.3M and `3225. As a result, the tubey corresponding Ato tube -Sll dires but the tube corresponding to tube 355 does not and the motorll is operated to `rotate shaft-35i? at a slow speed in one direc- -tion and lthrough the unity ratio gears 4,2I to applied to :the-winding of potentiometerfB-MPS over :a circuit from .thelilllp. bus -barthrougllthe vpotentiometer .Winding and resistance 409 -to ground. l.The potentiometerscontrolled byhaft `1i2."2--.Will `now .be adjusted to positions commensurate -with Vthe :altitude as determined ,byathe altimeter potentiometer APS orsince the airplane has :not 4taken off, `the barometric pressure-v at l seaslevel.

The; manifoldqpressure indicators, on the pilots. ight ",engineers and instructors instrument :fp anels will `be operated inthe manner .i'ullyzdisclosedand described inthe Lukaszandzqtrihler applicationihereinbeforet referredl to, thronghthe operation of the `autosyn gtnansmittertthe rotor of which is driven from the shaft 35D of the manifold pressure motor unit.

As soon as the- STM relay 8|@ operates, the circuit previously traced for applying potential of phase el to the signal input conductor lili of the manifold pressure motor control circuit is opened and a new circuit is established which extends from conductor 457, through resistance 406, over conductor 395, over the lower back contact of the EST! relay 8l3 and over the inner upper front Contact of the STM relay Si@ to a point between resistances 8M and SEE of the potential divider comprising such resistances, which potential divider is supplied with potential from the idol bus bar over a circuit extending from said bus bar through such resistances to ground. The potential now applied to conductor 491 is somewhat less than formerly applied due to the fact that the simulated engine is now assumed to be turning over under the control of the inertia starter and will therefore produce a suction in its manifold to reduce the manifold pressure slightly below the BO-inch barometric pressure.

With the potential ci phase qs! now applied to control conductor liti less than the balancing potential of phase p2 applied to conductor il? by the balancing potentiometer RMP5, the overbalancing potential of phase ft2 is effective to control the motor 35M to drive the shafts 35u 422 in such a direction as to move the sliders of the potentiometers driven by shaft 422 toward the No. l terminals of their windings indicative of a reduction in manifold pressure. The transmitting autosyn 355 driven by the shaft 350 also controls the operation of the manifold pressure indicators on the pilots, ight engineers and instructors instrument panels to show the reduced manifold pressure.

When the MAN relay @B5 released, as previously described, in response to the setting oi the propeller switch for automatic operation, circuits were established for applying potential of phase nl to the signal input conductors til@ and 532 of the RPM and propeller pitch motor control circuits from the llilqbl bus bar, over the inner upper iront contact of the STM! relay SSS, through resistance l to the junction point between resistances 8H and 8l8 interconnected over the upper front contact of the STM relay I Bill, and thence over the resistance network of parallelly connected resistances comprising resistances EN to 322, inclusive, resistance Elli of Fig. 6, and the winding of potentiometer RPPI.

The resistance M9 forms one parallel branch of the network, resistances 82B to 832 connected in series :form a second branch, resistance 663 forms a third branch and the winding of potentiometer RPPl forms a fourth branch. Resistances 8N, 820 and 5&3 and the winding of potentiometer RPP! each have one terminal connected to ground and thus the ground terminals of the branches are interconnected, and the other terminals of the branches are interconnected over conductor extending from the right terminal of resistance to the ungrounded terminal ci resistance @-93 and the slider of potentiometer RPPi, thence over conductor il'illl and the inner upper back contact of ivhe EST! relay SiS to the ungrounded terninal of resistance illu. The interconneeted ungrounded terminals of the parallel branches of the resistance network are connected from conductor S23 over the upper front contacts of the IGR and IGL relays Bill and Still, assumed to have been operated. ovgy me lower back contact of the MAN relay 835, through resistance 825 to the signal input conductor 532 of the propeller pitch motor control circuit of Fig. 5 and in parallel therewith over the upper front contact of the PRM relay 8H and the middle upper front contact of the STll/il relai7 399, conductor 356, through resistance 438 and to the signal input conductor Llull of the RPM motor control circuit of Fig. 3.

The potential of phase gbl applied over the resistance network to control conductor 532 of the propeller pitch motor control circuit is less than the potential of phase (p2 applied thereto as previously described and since the sliders of the potentiometers controlled by this motor control circuit have been moved to the N o. 1 terminals of their windings and the potential of phase (p2 still predominates over the potential of phase ol, the predominating potential of phase o2 will hold the RV! relay 533 operated and the LS relay 536 is thus maintained energized to prevent the motor 53d from moving the sliders of the potentiometers controlled thereby away from the No. 1 terminals of their windings.

The potential of phase p1 applied over the resistance network to control conductor du@ is amplified by the tube Sim and is impressed upon the control grids of tubes 304 and 3635 with the result that the tube 304 res'but tube 305 does not and consequently the RV and RVi relays SI2 and SiS are not operated and the motor 3M is operated in a direction to rotate the shaft Si@ and through the unity ratio gears liiil to rotate shaft M32 and the sliders of the potentiometers f controlled thereby away from the No. l terminals of their windings. The winding of balancing potentiometer RRP!!! is connected in parallel with resistance M0 and is energized' by potential of phase o2 supplied from the Mp2 bus bar through resistance dll. The potential of phase e2 derived from this potentiometer is applied from the slider thereof through resistance 4 l 2 to the signal input conductor 400 and when the slider of this potentiometer has been moved to a point such that the potential of phase 2 is exactly equal and opposite to the potential of phase I applied to conductor 400 as previously described, the amplifier tube 360 receives no signal potential and tube 381i no longer fires to cause the operation of the motor 3 ill. 'The sliders of all ofthe potentiometers controlled by the RPM motor control circuit have now been set to positions representative of the speed at which the inertia starter is turning over the right engine.'

As soon as shaft 3l il leaves its normal position, cam H5 mounted thereonpermits the operation of the limit switch L'I to its alternate position thereby establishing an obvious circuit for the on relay BIB which, upon operating prepares over its inner left contacts a reversing circuit through the stator circuit of the motor 3M and establishes a start circuit overconductor 3l8 for starting the tachometer motor control circuit (not shown). This latter control circuit functions in the manner fully disclosed in the application of Lukacs and Strickler hereinbefore referred to, to control the operation of the tachometers on' the pilots, flight engineers and instructcrs instrument panels'to indicate the speed at which the engine is being turned over by the inertia starter. Relay 3I6 also establishes a circuit from groundover its middle left contacts and over conductor 319 to battery through the winding of the RPM relay 826 of the engine control circuit of Fig. 8 and establishes a further circuit-from-'grund- Iover itsoutenleft contacts and conductor' 32) to the temperature and pressure circuit (not shown) appertaining to the simulated rightengine,y whichI then functions in the manner fully described in the application of Lukacs and'fStrickler'hereinbefore referred to.

They STMl yrelay 899 upon operating is also effectiv'toY establish a circuit for starting the sound effects circuit (not shown) to produce' noises' simulating' the'f operation' of the er1-gine; Thern'anner in'whic'h these-sound effects are pr'o'- duced-is fullydisclosed in the Lukacs and Strickler application'hereinbefore referred to.

It bein'g assumed -that the night engineer has previouslyf` operatedthe fuel selector Valve for` v supplying fuel'ffrom' the right hull tankto the rightengin'e and vthat the RF' relay 72! of Fig'. '7 has-operated indicative of the' fact that fuel lis availablefr the' right engine, then a circuit is established'to start' theelectrically-driven fuel; pressureffpump'ftof produce fuel pressure in the' establishedfor'fthe'start relay 'F23 of the fuel pressurermot'or unit whichr relay uponV operating establishes4` a' circuit through 'the rotor of the motor''lll;tlf11o'ii-,=,flrresistancel 125, over the upper back'contact ofthe'UL relay 725', over the upper' frontfcontact ofiheST relay'l23 and over the backcontact ofithe" DFP relay i2l 'to the source of phase lelwcurrent supplied from the upper portionofl' the divided' secondary winding' of the power transformer '128;` The stator winding T129' of thei=1notor1124ris supplied with phase? p2 potential fromfitheflower p'o'rtion of thesecondary windingof'th'elpower transformer 128 andthe motorf'124l consequently drives the shaft 130 through'thef-reductionfgear'box i3-'I in suclradiL-'f rectionfa's'-'to"cause the ca'm' '132 'carried 'by the shaft'fto'- rotate in-a counterclockwise direction and1to`=thereby1permit a'fclosure of the contact springsfassociate'd' with" suchy 'cam and the 'consequent' operation-'of theLL relay 33.

With?relay133'opera"ted indicative of the fact thatfuerpressure' inr the fuel linev supplying the righten'ginehas n'ow'beensimulated, with ignition relaysl 800l and '80! operated' indicative of the fact that the ignition 'key for the right engine has been operated, withy the PRM relay 8H operated indicative"- of the fact that the engine priming `switch has'been operated and with thefRP-Mfrelaytz operatedindicative of the factthatithengine' isbeing turnedover by theinertiafistart'er, the right engine should start and'l begin todevelop power; The EST! relay 8l 3 is operated ifthese-startingl conditions have been' fulfilled` 'over a `circuit which may be traced from ground overl theV inner upper front contacts of relays 8002an-d80 I; overcon'ductor' B21, over normally--closed lcont'acts lofA the right engine disable key. 1221 atffthe vinstructc' 1"sdesk, over the lower" contacts'of the LLrelay. '133 of the fuel pressure motor' unit.- over' conductor 82B, over the inner lower back: contactoftheFIR relay 329, over' the-lower front contactof the PRM relay Sil.' over thefront l'contactof the RPM relay 826 and to battery through'thewinding of the ESTI relay 8l3;` Underfthe'condition which would exist if theengine-'hadfbeenl previously operating and primrngizavould therefore-be unnecessary and the The operation of the' 12 PRM- relayr'l I -wouldfnot therefore be operated, the circuit just traced would extend over/the normal-contacts of the ICOI yrelay rather than over' the-lower contactsof relay 8l i.

Relay v 8i 3 y upon operating establishes` overy its inner'lowerfront contactan obvious circuit for the ESTA'relay 830 which operates and in turn establishes over its inner lower front contact- Relay' an obvious-circuit for the EST relay 83|. @Si upon-'operating establishes' a circuit for the' RFS relay136 at yth'eflight engineers station over a circuit which may be traced from ground, over the uppercontactslof the' RF relay 12|, over conf ductorrlll;over'thel'innerfright contacts of the ON relay-316 of-the RPM motor control circuit,

over" conductor 321; overy the 'inner upper' con'- tacts lofrthe ESTv relay 8'3l and conductor 832 to batterythrough the winding of the RFS relay 736;A Relay 1`36ithereupon operates in turn caus-V ing the operationorthe RFS! relay` 'Iv'lwhichv supplies an vauxiliar-y operating circuitA for the ST relayvof the fuelpressuremotor unit to insure` that this motor unit -willcontinue toi simulate fuel pressure during intervals when the ighten# frineeris' operatinghis fuelV selector'valve tol 'switch the-fuelfnfeed1inefromrone tank to' another as fully' described-'in the'v Lukacs" and Stricklerapplication --h'ere'iifbe'ine` referred to.

As-soonl-asthe'EST relay83l operates;` it opens the circuit' Oflthey S'IWirelayf which in turn?" releasesi the' STM-l relay 809, followed by the:

STM` relay BMJ* ifI the4 flight engineer has not in the meantime restored the enginestart key to its normaly position l'after 'observing from'thev ta'- chometerfandnthe-increased engine noise that theengineiishrunningunder its 'ow-n' power. 89upon1-releasing also opens the locking circuit of the PRM relay''ll which nov/'restores since it is assumed that the primingfswitchfwas only niomentarilyl operatedfby the flight engineer to prime the engine and thusthe initial operating circuit ofhrelayf` '8 I has been opened.

Withx'the STM,` STMIv and PRM'relays 8m; il'and8-l|-released and theESTl relay 813 opstated',` new-` circuits arefestabli'shed for' applying signalf potential* of phase'` ol to the signal' input conductor' '532'1of'the 'propeller pitch motor controlffcircuitytothe-signal in'put conductor 409 of thelRPM: motorfcontol' circuit` and to theI signal" inputf conductor-'401 of the' manifoldy pressure motor 'control circuit.

PotentialII-ofphasef p'l is' applied tothe signalinput conductors'dfand f532 of the RPM and propeller' pitch` motor control circuits from the QQrpl busbar; over thewmiddle' upper front con tact o-the'ESTl r'elay"8-l3,A over conductor 835,' throughI resistance vil l 3 tofthe' resistance network of parallelly connected resistancescomprising resistances'-f320ito-822; inclusive, resistance 603 Relay tiometer RMP! is wound with higher resistance wire than the remaining 75 per cent and is shunted by the variable shunt including the throttle controlled rheostat N35 and the adjustable resistance comprising the series-connected resistances 4i4 to 4i?, inclusive. Resistances B2i! and 603 and the windings oi potentiometers RPPi and TASP5 each have one terminal connected to ground and thus the grounded terminals of the branches are interconnected and the other terminals of the branches are interconnected over conductor E323 extending from the right terminal of resistance 322 to the ungrounded terminal of resistance 5&3 and the slider of potentiometer RPPl, thence over conductor 824 and the inner upper front contact of the ES'lli relay m3, over conductor all!! to the slider of potentiometer RMPI, through the left portion oi the winding of such potentiometer to the slider of potentiometer TASP5 throt1 l1 the left portion of the winding thereof to its ounded terminal. The interconnected ungrounded terminals of the parallel branches of the resistance network are connected from conductor Sie, over the upper front contact of the IGR IGL relays sul and 8594, assumed to have been operated, over the lower back contact of the MAN relay MSE, through resistance 825 to the signal input conductor 532 of the propeller pitch motor control circuit of Fig. 5, and in parallel therewith over the upper back contact of the ICO relay Ba. over the upper back contact oi the PRM relay @l i and over the upper iront contact oi the ESTl relay cl3, conductor 856, through resistance 53B to the signal input conductor lull of the RPM motor control circuit of Fig. 3.

At this time the slider oi the propeller pitch potentiometer RPPi is at the No. l terminal of its winding since, as previously described, the propeller pitch has been. assumed to have been set for maximum RPM where?` 1 its maximum sistance or 10.000 ohms is included in its branch of the network, the slider of the true sneed. potentiometer TASP is at the ilo. l. terminal of its winding since at this time the air zero, the slider oi the throttle rheostat 'H35 s at the No. 1 terminal oi its winding since the throttle is at this time closed and the slider the manifold pressure potentiometer RMPl is at a position on its winding corresponding to the i manifold pressure produced oy the suction on the manifold at the time the engine starts. Such ones of the resistances dill, Mii and Lili' are included in the shunt oi the left cent of the winding of manifold rressure potentiometer RMP! as is necessary to make the re stance ci the branch of the network including tl. vinding of potentiometer RMT! s1 "h that with the air speed Zero. with the ler pitch set for the maximum RPM and the throttle closed, the potential of phase el applied to the signal input conductor till! will be such as to cause the RPM motor control circuit to adjust the potentiometers controlled thereby until the tachorneters on the pilots, flight engineers instructors instrument panels show idling speed of 450 rev'- olutions per minute, As the engine speed increases, the manifold pressure will also change and this change is introduced by the adjustment of the manifold pressure potentiometer RllTi included in the control of the RPM motor control circuit as will be presently described.

The potential oi phase gbl applied over the resistance network to the control conductor 532 of the propeller pitch motor control circuit is still less than the potential of phase p2 applied thereto under the control of the propeller governor rheostat 'H5 as previously described and, since the -sliders of the potentiometers controlled by this motor control circuit have been moved to the No. 1 terminals of their windings and the potentiel of phase e2 still predominates over the potential of phase el, the predominating potential of phase e2 will hold the RVi relay dit operated. The LS relay 535i is thus maintained energized to prevent the motor 534 from moving the sliders of the potentiometers controlled thereby away ironL "ne No. l terminals of their windings.

Following the operation of the EST! relay Slt, the circuit over which potential of phase l was applied to the signal input conductor lill of the manifold pressure moto-r control circuit is changed -so that this circuit is controlled to show changes in the manifold pressure in response to throttle opening, to RPM, to the altitude at which the ilight is conducted and to the speed at which the supercharger blower is assumed to be operaled. The major control of the manifold pressure motor control circuit is now exercised by the application of potential of phase qb! derived from the throttle-controlled rheostat lill, the winding of which is energized from the wel bus bar over conductor 7355, which potential is applied from the slider of such rheostat over conductor its, through the winding of the altitude potentiometer APt and resistance 42d to ground. Potential derived from the slider of potentiometer AP4 is then applied over conductor 439, over the outer right contacts of the ON relay 345 of the RPM motor control circuit of Fig. 3, over conductor 44H over the upper back contact of the SI-IRl relay 424 (which is at the time deenergized since the iiight engineer has, as previously described, operated the supercharger blower speed control into its low speed position), through the RPM potentiometer RRP5, over the middle upper baci; contact of relay 424 to the junction point between resistances 425 and i125. The resistance 425 is connected over the lower back contact oi relay and conductor lll with the No. 1 terminal of the manifold pressure rheostat 742 at the instructors desk, Fig. 7, the No. 3 terminal of which rheostat is connected to ground. One terminal of resistance 426 is also connected to ground. The potential of phase qs! applied to the junction point between resistances 25 and 42E is thus attenuated over the path through resistance 42% to ground and also over the path through resistance 425 and the winding of rheostat 'E42 to ground and the potential derived from the slider oi rheostat T42 now becomes applied over condoctor 'M3 and the lower `front contact of the RSTI relay 853, over conducto-r 465 and through resistance @lili to the signal input conducto-r 4M. lt is to be noted, however, that with the throttle in its closed position the slider of the throttlecontrolled rheostat 'lill is at the No. l or grounded terminal of it-s winding and consequently no signal potential is applied over the circuit just traced to the signal input conductor 4M.

At the same time potential of phase el which is applied' from the wel bus bar over conductor 'E38 through resistance 7M' to the slider ci the throttle controlled rheostat lll@ (the winding of which is shunted by the resistance 7&5 and the No. l. terminal of which winding is connected to ground) is applied over conductor i 42T through the winding of the RPM potentiometer RRPS to ground. The potential derived at the slider of the RPM'potentiometer RRPS is applied over conductor 428, over the middlelower front Contact of the ESTi relay 813, over conductor i129y and through resistance li to the signal inn put Conductor fil' of the manifold pressure motor control circuit. With the throttle in its closed position and consequently with the slider of the throttieco? rolled rheostat 'i'i at the No. l terminal of its winding, potential of phase qbi is applied over the circuit just traced to control conductor il''i Which potential decreases as the RPM increases from the speed at which the engine was turned over by the inertia starter to the idling speed o-f 45@ revolutions pe: minute and the slider of the RPM potentiometer RRPS moves toward the No. 3 terminal of its winding.

As the potential of phase i thus applied to the control conductor S1 decreases, the potential of phase o2 applied as previously described to conductor Gl from the balancing potentiometer RMP5 overbalances the signal potential of phase oi and as a consequence the motor 354 is controlled by the manifold pressure motor control circuit to rotate the shaft i322 in such a direction as to move the sliders of the potentiometers controlled thereby toward the No. l terminals of their windings. This movement of the slider` of potentiometer RlVIP results in a de crease of the potential of phase p2 applied to Conductor @Si until it again balances the signal potential of phase el applied through the RPM potentiometer RRP@ as previously described, when the slider of potentiometer RRP3 comes to rest indicative of an engine idling speed of 450 revolutions per minute. The sliders of the manifold pressure potentiometers will now have been adjusted to positions indicative of an idling manifold pressure of approximately 10 inches of mercury and this pressure will'be indicated on the manifold pressure indicators on the pilots', ight engneers and instructors instrument panels.

The effect of change inmanifold pressure is a factor in determining the RPM of the engine This effect is introduced as previously stated upon the signal input conductor GSB of the RPM motor control circuit by the positioning of the slider of the RMP potentiometer. The movements of the shafts 92 and i522 of the RPM and manifold pressure motor unitsi commensurate with the idling speed of the engine and the consequent change in the manifold pressure, also i affect the fuel flow circuit (not shown) in the manner fully set forth in the application or Lukacs and Strickler hereinbefore referred to. As the elia? S2 is rotated to show an increased simulated engine speed, the sound effects circuit is controlled to produce sounds indicative of the increased speed.

When the shaft 310 of the RPM motor unit has been rotated to a position corresponding to a speed of approximately 400 revolutions per minute, the contacts of the switch V are closed by the cam 322 mounted on the shaft 3H) to establish a circuit from the 115-volt bus bar I |5q 2 over contacts of the switch V and conductor 323 to ground through the winding of the variac RRVG from which power is derived for driving the vibrator -motor (not shown) connected to the right side of the trainer mockup. The shaft of this motor carries an eccentrically mounted Weight whereby the vibration set up in the rightl portion of the mock-up simulates the vibration due to the propeller driven by the right engine. This vibration increases as the right engine speed increases.

The EST relay 83! upon operating'establishes a circuit from-tlnaflliqslVv bus bar over its upper contacts to a point in-'the potential divider ex-Y tending from ground through resistances' 831 and S33, c-ver the upperY back contact of` the LN relay 832, over conductor 840, through the Wind-v ing of the manifold pressure' potentiometer RMP@ and resistance 203 to ground. A potential determined by the position assumed' by' the slider of potentiometer RMP4 is applied over conductor 284', over the middle lower back con-Y tact of the SHR relay 423, through resistancev liti, over conductor 432 to the slider of the RPMl potentiometer RRPI and over the potential divider extending from ground through the-po` tsntionseter winding, over conductor 205. over the lower back contactA of the SHRV relayV 423,- through resistances l33and 434 'to ground, andfin parallel with the latter circuit divider through' resistance 20E to the signal input conductor 201 of the brake horsepower motor controlfcircuit- Po' tential is also applied-from the junction pointy between the'back contact ofthe LN relayy 839' of Fig. l appertaining to the right engine.

and resistance 838,' over' the inner upper front contact of the ESTA relay 830, over conductor 813i, through resistance 208 andthe winding of' the altimeter potentiometer AP2 to' ground and the potential derived at the slider of this potentiometer is applied through resistance 29 lto Vthe .signal inputI conductor 261'.

The brake horse-power motor' control'circut' is thereby controlled to rotate the shaft ISUVand through the unity ratio bevel gearsv 2 I0 to rotate i RBPiEl is derived from the winding of the po' tentiometer whichis energized in a circuit from the bus bar Mp2, throughl resistance 2|3 andthrough the winding of such' potentiometer a'nd resistance 2M to ground. The brake horse-power therefore varies in accordance with the equation BHP: [(MP) XJ(RPM) X (MIXTURE)] -i-f(ALT) -F(ENGINE) the resistance network is so designed that a' further increase in RPM, as indicated by the movement of the slider of potentiometer RRPI, then causes a decrease in brake horse-power as would be the case in an aircraft.

The operation of the propeller pitch m'otorY control circuit as previously described has resulted in the' movement of'the slider of the RPP3 potentiometer to the No. 1 terminal of its win'ding. The true air speed v'ariacTASVl is so arl'v ranged that with the air speed indicators' of the trainer showing zero air speed, the slider of this variac will normally stand in a position with respect to its winding corresponding to an air' speed of approximately 48 knots. Consequently with the Winding ofethefvariacenergizedby-"po Thev poten--` tial of phase 2'over the slider' of potentiometer" tential of phase o2 from the 4U2 bus bar, potential of phase p2 is derived at the slider of the variac and applied through the propeller pitch potentiometer RPP3, through resistance 22! to ground and through resistance 222 to the signal input conductor 220 of the propeller slip ratio motor control circuit of Fig. 1. This potential will be instrumental in operating the motor I l2 of this motor control circuit in such a direction as to hold the sliders of the potentiometers controlled thereby at the No. 1 terminals of their windings.

As soon, however, as the RPM motor control circuit of Fig. 3 is operated in simulation of the starting of the right engine, and the. slider of the potentiometer RRPZ operated thereby moves away from its No. 1 or grounded terminal, potential of phase qll will be applied to the signal input conductor 220. To accomplish this, potential of phase el is applied from bus bar 40| through resistance 2H and through resistance 2i8 and the Winding of the propeller slip ratio potentiometer RPS connected in parallel to ground, the potential derived at the slider of this potentiometer being applied through the winding of the RPM potentiometer RRP2 to ground and the potential of phase derived at the slider of the latter potentiometer being applied through resistance 2|9 to conductor 22B. However, until the RPM potentiometer RRP2 is adjusted to a position indicative lof an engine speed above the idling speed of 450 revolutions per minute, the potential of phase ol applied thereover will not overcome the potential of phase o2 `applied under the control of the true air speed variac TASVI and the sliders of the propeller slip ratio potentiometers lwill not therefore move away from the No. 1 terminals of their windings.

Equipment (not shown) for simulating the left engine is identical With that disclosed for simulating the right engine and is operated to simulate the starting of the left engine in the manner just described resulting in the control of the manifold pressure, RPM, tachometer, propeller pitch, brake horse-power, propeller slip ratio, fuel flow and fuel pressure motor units appertaining to the left engine; in the operation of the instruments on the instrument panels to indicate the engine speed and manifold pressure and in the control of the sound effects and vibrator circuits to simulate the engine noise and propeller vibration.

As a result of the operation of the brake horsepower motor control circuit for the left engine, the motor |42 thereof rotates the shaft i110l and through the unity ratio bevel gears 223 rotates the shaft 224 to position the sliders of the poteniometers driven thereby in positions commensurate with the Ibrake horse-power output of the left engine at the assumed idling speed of 450 revolutions per minute. `As a result of the operation of the propeller slip ratio motor control circuit for the left engine, the motor |22 thereof rotates the shaft 120 and through the unity ratio bevel gears 225 rotates the shaft 226 to hold .the sliders of the potentiometers driven thereby on the No. 1 terminal ends of their windings.

With both engines running, circuits are established for controlling the thrust ,horse-.power motor control circuit of Fig. 5. One of these control circuits extends from the slider of lbraise horse-power 'variac RBV'I for the right .engine (the ywinding of which is energized by current from the 4D`I bus bar), through resistance y601i to the sliders of the propeller sli-p ratio potentiometers RPS! and REST; and through resistance finito the signal input conductor 606 of the thrust horse-power motor control circuit. A second control circuit extends from the slider of brake horse-power varian LBVT for the left engine (the winding of which is energized by current from the 40M bus bar), through resistance 601 to thev sliders of the propeller slip ratio potentometers LPS@ and LPS'I and through resistance 608 tothe signal input conductor 606. However, with the engines idling and the sliders of the propeller Aslip ratio potentiometers RPSS, RPSI, LPSS and LPST at the No. 1 terminals of their windings indicative of a zero slip ratio, no potential will beappled. over the circuits just traced to conductor f'lland the thrust horse-power control circuit is'notr operated, thereby representing the ldevelopment of no lthrust horse-power by the propellers..

To prepare fory a simulated take-off, with the propeller governorcontrols for the engines set into their MAX-RPM positions in which the sliders of the rheostats controlled thereby are moved to the No. 3 terminals of their windings. the pilot moves the. two .engine throttles together to move the sliders of therheostats controlled thereby toward their upper or open throttle positions. In response to the movement of the slider of the throttle-controlled rheostat for the right engine, the resistance of the shunt through the Winding of rheostat M5 over conductors M8 and M9 and through resistance 4l4 and the selected portion of the grou-p of resistances M5 to lill, inclusive, will be increased and more of the potential of phase pl applied over conductor 835, through'resistance H3', through the winding of potentiometer RMP! to ground will be available at the slider of .potentiometer RMPI, and the potential applied to the signal input conductors 400 andf532 of the RPM and the propeller pitch motor control circuits for the right engine wi11 be increased, `As a consequence the RPM motor control circuit will rotate the shaft 1502 and thereby the sliders of the potentiometers and variaes .controlied thereby to an amount representative of an increase of the ,RPM of the right engine. Responsive to'this operation, a potentiometer (not-shown) driven by .the shaft 4oz controls the taehometer motor control circuit to cause the tachorneters `on the pilots, flight eneineers and instructors instrument panels to indicate an increase of! engine speed.

As the right engine throttle is opened, the noten-tial of phase el applied over the `resistance network to control conductor 32 of the propeller pitch motor control circuit for the right engine is increased but still less than the potential of phase '1,752 applied 'towntwl conductor 53.2 as previously described. and .consequently the motor 534 is not operated .te drive the sliders of the potentiometers controlled there-by .away from the No. l :terminals o their windings,`

In a similar manner. RPM motor control circuit for the left engine :responds to .the opening of the left engi-ne throttle. As just described, .the .sliders oi thepoientiometers driven by the motor of the propeller pitch motor control circuit for the left engine rem-ain positioned at the No. l terminals of windings. The ,engine throttles are thus operated unt-il the tachometers for the two liaxidiclate .engine .speeds of .1900 revolutlenspcr xrltllute. ,ets the engine .speeds increase, the manifoldvpressures .oi the .engines increaseuntil the manifoldpressme indica. tors show read-ings ot-i2? inches of mercury.

With the engines both running at the indicated speed of 1900 revolutions per minute, the pilot checks to determine if both of the magnetos associated with each engine are functioning properly. Considering the engine control circuit relating to the right engine, the pilot rst turns the right engine ignition key '|02 (Fig. 7 to the position in which ground is removed from its right magneto terminal but remains connected to the left magneto terminal. This causes the shunting down of the IGL relay 800 of Fig. 8 resulting in the removal of resistances 32| and 822 from the branch of the resistance network over which potential of phase ol was applied to the signal input conductors 400 and 532 of the RPM and propeller pitch motor control circuits and the rotation of shaft 402 driven by themotor 3I4 of the RPM motor control circuit in a direction in which the tachometers on the pilots, flight engineer's and instructors instrument panels show a decrease of indicated RPM to 1800 or 1850 revolutions per minute. The ignition key '|02 is now turned to the position in which ground is removed from the left magneto terminal but is connected to the right magneto terminal. This causes the reenergization of the IGL relay 800 and the shunting down of the IGR relay 80| resulting in the removal of resistance 822 from the branch of the resistance network over which potential of phase was applied to the signal input conductors 400 and 532. No change in the indicated RPM will now be noted if both magnetos are functioning. The ignition key is then moved to the position in which the IGL and IGR relays 800 and 80| are both operated resultingin the operation of the tachometers to read 1900 revolutions per minute. These operations are then repeated for the left engine.

The pilot now gradually moves both throttle controls forward whereby the sliders of the rheostats controlled thereby are moved further toward their upper or open throttle positions. As a result the RPM motor control circuits for the two engines are controlled to move the shafts, such as 402, to new positions whereby the tachometers on the instrument panels show a further increase in the engine speeds.

In response to the movement of the sliders 0f the throttle controlled rheostats '|06 and '|01 for the right engine toward the upper terminals of their windings, the potential of phase qb| applied from the slider of rheostat 'I6 over the circuit previously traced to the signal input conductor 40'! of the manifold pressure motor control circuit for the right engine, is increased. This potential not only increases with the throttle opening but also increases with the increase of RPM also resulting from the throttle opening as previously described. At the same time the potential of phase applied from the slider of the throttle controlled rheostat '|01 over the circuit previously traced to the signal input conductor 40'! of the manifold pressure motor control circuit for the right engine will increase. As a result, the manifold pressure motor control circuit will function to control the movements of the shafts 35D and 422 into new positions resulting in the setting of the transmitting autosyn 355 to control the operation of the manifold pressure indicators on the instrument panels to indicate an increase of manifold pressure for the right engine to about 44 inches of mercury. The manifold pressure motor control circuit for the left engine (not shown) -is similarly controlled in response to the operation of the left engine 20 throttle whereby the left engine manifold pressure indicators on the instrument panels also show an increase in manifold pressure to 44 inches of mercury.

With the increase in manifold pressure the engines will develop enough power to cause the airplane to move through the water and to pick up air speed. In the trainer as the sliders of the throttle controlled rheostats approach their upper or open throttle positions, the potentials of phase pl applied to the signal input conductors of the propeller pitch motor control circuits increase until such potentials become slightly greater than the potentials of phase p2 applied to such conductors under the control of the propeller governor rheostats and such motor control circuits will operate to adjust the potentiometers controlled thereby into positions indicative of a change of propeller pitch. For example, when the potential of phase pl applied to con trol conductor 532 of the propeller pitch motor control circuit for the right engine, applied under the control of the throttle rheostat 105, becomes greater than the potential of phase Q52 applied to conductor 532 under the control of the propeller governor rheostat 5, the motor 534 is operated to rotate shaft 530 and through the gears 62| to rotate shaft 622 in a direction to move the sliders of the potentiometers controlled thereby away from the No. l terminals of their windings.

As a result of the movement of the slider of potentiometer RPPI, the resistance of the branch of the resistance network including the winding of such potentiometer is decreased resulting in a decrease in the phase potential applied to the control conductor 532 until it again becomes equal to the potential of phase 2 applied to control conductor 532 by the propeller governor rheostat H5. The reduction by the propeller pitch potentiometer RPPI of the potential applied to the signal input conductor 400 of the RPM motor control circuit will result in the limiting of the potential of phase applied to the control conductor 400 to a value which will not permit the motor thereof to adjust the potentiometers controlled thereby to positions indicative of an engine speed greater than that called for by the setting -of the propeller governor which has been set for MAX-RPM for an engine speed of 2600 revolutions per minute. The resistance introduced into one branch of the resistance network by the throttle controlled rheostat |05 increases as the throttle is opened beyond 50 per cent opening thereby tending to increase the potential of phase applied to the signal input conductor 400 to a Value which would produce a speed indication of greater than 2600 revolutions per .minute but the propeller pitch potentiometer RPPI reduces the resistance of another branch of the resistance network to reduce the potential of phase applied to the conductor 400.

As the speed and manifold pressure of the simulated right engine increase, the RPM potentiometer RRPI and the manifold pressure potentiometer RMPI are affected to cause an increase in the potential of phase applied to the signal input conductor 201 of the brake horsepower motor control circuit for the right engine, whereupon the motor of this circuit is controlled to adjust the potentiometers driven by the shafts |30 and 2|| into new positions representative of the horse-power developed by the right engine at the indicated speed of 2600 revolutions per minute and at the indicated manifold pressure of 44 inches of mercury. The brake horse-power motor control circuit'for the left engine is simi-"- larly controlled.

A further result of the increase of the simulated engine speed and the simulated increase in the propeller pitch by the movement of the sliders of the propeller pitch potentiometers away from the No. 1 or minimum pitch positions is the readjustment of the potentiometers of the propeller slip ratio motor unit to new settings representative of the propeller eniciency at the new speed, which propeller efliciency is a factor in determining the thrust horsepower output of the propeller. The propeller slip ratio may be expressed by the equation PSR=1 NrmPPi where V is the true air speed PP is the propeller pitch N is the number of turns per minutes made by the propeller D is the diameter of the propeller.

From the foregoing equation, it will appear that the propeller slip 'ratio varies directly as the true air speed, inversely as the RPM and inversely as the propeller pitch. The vintegration of this equation may be approximated closely enough for the purposes of the invention by the circuits shown in the upper portion 'ofl Fig. 2 'in which the function V is introduced by the true air speed variac TASVI, the function N is introduced by the RPM potentiometer RRP2 and the function PP is introduced by the propeller pitch Y potentiometer RPP3.

It will be recalled that potential of `phase o2 is applied to the signal input conductor 220 of the propeller slip ratio motor control circuit under the control of the true air speed variac TASVI and yunder the control of the propeller pitch p0- tentiometer RPP3 and that potential of phase gbl is applied to conductor 220 under the control of the RPM potentiometer RRP! and the Apropeller slip ratio balancing potentiometer RPSS f and that until the engine speed was increased above the idling speed, with the sliderof potentiometer RPPS at the No. 1 terminal of its winding, the potential of phase o2 predominated on control conductor 220 to hold the sliders of the propeller slip ratio potentiometers from lac'ivancing away from the No. 1 terminals of their windings.

As the speed of the engine increases to 2600 revolutions per minute, the slider of vthe RPM potentiometer RRP: is advanced toward the No. 3 terminal of its winding 'thereby increasing the potential of .phase pl applied to ycontrol conductor 229. Also as the propeller pitch is increased the slider of the propeller pitch potentiometer RPP3 is advanced away from the No. 1 terminal of its winding, thereby decreasing the potential of phase p2 applied to conductor 220. As a result of the summation oi these potentials, the motor H2 of the propeller slip ratio motor control circuit operates to rotate shaft 216 in such a direction as to move the sliders 'of the potentiometers controlled thereby towards the No. 3 terminals of their windings. As the slider lof potentiometer RPSB advances over its Winding, `the potential of phase al applied thereover to control conductor 22B becomes reduced until it balances the potential of phase 2 atwhich time the motor will stop and potentiometers R'Pst andRPSl will have been adusted to positions commensurate with the propeller emciency 'at the assizimedv speed of 2600 revolutions per minute and at the as sumed propeller pitch.

As the sliders of potentiometers RPSS and RPSI move away from the No. 1 terminals of their windings, their combined resistance to ground first increases from zero to a maximum when the sliders have moved about 30 degrees away from their No. 1 terminals and then as the sliders advance further, the combined resistance decreases again to zero. As the resistance increases the phase pl ypotential derived at the slider of the brake horse-power variac RPVI which is available for application to the signal input conductor Eile of the thrust horse-power motor control circuit increases. In a similar manner as the RPM of the left engine increases the propeller slip ratio motor control circuit appertaining to the left engine propeller is coritrolled to advance the sliders of the potentiomete'rs controlled thereby away from the No. 1 terminals of their windings and the potentiometers LPS@ and LPSl cause rst an increase and then a decrease in the potential of phase qb! Yderived at the slider of the left engine brake horsepower variac LBVl and applied to the control conductor 606.

The summation of the potentials of phase gbl applied to the signal input conductor 606 of the thrust horse-power motor control circuit is determined by the brake horse-power outputs of the engines as modiiied by the eiiciency of the propellers which they drive. In response to the summation of these potentials the thrust horse-f power motor control circuit causes the motor 5|2 thereof to drive the shaft Sit and through the unity ratio bevel gears 'elle to drive the shaft Sill until the slider of the balancing potentiometer IPill driven by the shaft 6H) has assumed such a position that the potential of phase p2 applied thereover and through resistance Ell to control conductor 606 balances the summation of the phase pl potentials applied to conductor 886. When this :condition of balance is reached the motor stops. The winding of potentiometer TPS is energized by potential of phase 2 applied from the 4il2 bus bar through resistance @l2 and 'the winding of the potentiometer in parallel with resistance l to ground.

As fully described in the application of Lukacs and Strickler hereinbefore referred to, potentiometers driven from the shaft 6| il of the thrust horse-.power motor unit are effective to control the indicated air speed and in turn the true air speed motor control circuits of the trainer to indicate that in response to the full opening of the engine throttles, the movement of the aire craft over the water is being simulated. With the increase in true air speed the slider of the true air speed varac TASVI is moved further toward the No` 4 terminal of its Winding thereby increasing the'potential of phase a2 applied to the control conductor 220 of the propeller slip ratio motor control circuit. Since, however, the engine RPM has been increasing at the same time to produce the increasing air speed, the slider of the RPM potentiometer RRP2 Willbe advanced toward the No. 3 terminal of its Winding to cause an increase in the potential of phase il applied to the control conductor 22D and with the increase of engine speed the propeller pitch potentiometer RPPS will hav-e become adjusted in response to the operation of the propeller pitch motor control circuit to simulate vthe adjustment of the propeller pitch to prevent the engine speed from'exceeding A2600 revolutions per minute re# 23 grdless of the amount of throttle opening. As a consequence the changing potentials of phase pl and phase 2 applied to control conductor 220 will tend to balance each other and prevent the operation of the propeller slip ratio motor control circuit.

However, should the engine speed represented by the potentiometer RRP?! increase at a rate faster than the rate of increase in true air speed represented by the variac TASVl, then the potential of phase el applied to conductor 220 under the. control of potentiometer RRPZ will increase at a faster rate than the potential of phase i112 applied to conductor 220 under the control of varias TASVI and the propeller slip ratio motor control circuit will operate to advance the sliders of the potentiometers operated thereby towards the No. 1 terminals of their windings indicative of a reduction in the propeller efficiency, which will, through the potentiometers RPSl and RPSl, cause the reduction in the thrust horse-power output and consequently a reduction in the indicated air speed.

When an air speed sucient for take-off has been attained the altimeter of the trainer will indicate that the take-olf has been simulated. For most efficient climbing in the type of airplane which is being simulated, engine speeds of 2400 revolutions per minute at manifold pressures of about 38 inches of mercury are required. To simulate these conditions the pilot reduces the throttle openings. The reduction of the throttle opening for the right engine reduces the potential of phase gbl applied as previously described under the control of the throttle controlled rheostats 106 and 101 to the signal input control conductor 401 of the manifold pressure motor control circuit whereupon the motor 354 thereof is operated by the predominating potential of phase (p2 applied over the balancing potentiometer RMP5 to move the sliders of the potentiometers driven by the shaft 422 until the potential of phase p2 applied by the potentiometer RMP5 balances the signal potential of phase pl. At such time the motor 354 will have adjusted the potentiometers driven thereby to positions indicative of the reduction in manifold pressure incident to the reduction in throttle opening. Manifold pressure indicators on the instrument panels will now show the reduced manifold pressure of the right engine. The reduction of the throttle opening for the left engine causes the manifold pressure motor control circuit for the left engine (not shown) to function similarly. The pilot will continue the gradual closures of the engine throttles until the manifold pressure indicators show manifold pressures for the two engines of about 38 inches of mercury.

The reduction in the throttle openings at the same time reduces the engine speeds as indicated by the tachometers on the instrument panels. For example, in response to the reduction of the throttle opening for the right engine, the throttle controlled rheostat 105 is effective to cause a decrease in the phase potential applied to the signal input conductors 400 and 532 of the RPM and propeller pitch motor control circuits. The decrease in potential of phase pl applied to the signal input conductor 400 results in the potential of phase 2 applied to such conductor by the balancing potentiometer RRPIO controlling the motor 3| 4 of the RPM motor control circuit to move the sliders of the potentiometers and variacs driven by the shaft 402 toward the No. 1 terminals of their windings indicative of a reduction in the speed of the right engine. The decrease in potential of phase pl applied to the signal input conductor 532 results in the potential of phase p2 applied to such conductor under the control of the propeller governor rheostat H5 controlling the motor 534 of the propeller pitch motor control circuit to move the sliders of the potentiometers driven by the shaft 622 toward the No. 1 terminals of their windings indicative of a reduction in propeller pitch which, under the control of the propeller pitch potentiometer RPPI, would tend to maintain the engine speed at the speed of 2600 revolutions per minute called for by the instant setting of the propeller governor control 100. In a similar manner the RPM and propeller pitch motor control circuits appertaining to the left engine are controlled in response to the operation of the left engine throttle.

To simulate the reduction of the engine speeds to the most ecient speeds of 2400 revolutions per minute for climbing, the pilot operates the propeller governor controls toward their reduced RPM positions. The readjustrnent of the governor control T00 for the right engine moves the slider of rheostat 'H5 away from the No. 3 terminal of its winding thereby decreasing the potential of phase 'p2 applied thereover to the signal input conductor 532 of the propeller pitch motor control circuit. With the right engine throttle previously operated to a position in which the manifold pressure indication is 38 inches of mercury and the potential of phase applied to control conductor 532 under the control of the throttle control rheostat |05 thus reduced, the motor 534 of the propeller pitch motor control circuit will be controlled to move the sliders of the potentiometers driven thereby until the slider of potentiometer RPPI reaches a position in which the potential of phase 45| balances the potential of phase Q52 when the motor will stop. The propeller governor control is thus adjusted to a position in which the slider of potentiometer RPPI is moved to a position in which the potential of phase I applied to the signal input conductor 400 of the RPM motor control circuit is such as to cause the latter circuit to set the sliders of the potentiometers controlled thereby into positions in which the right engine tachometers indicate an engine speed of 2400 revolutions per minute. The adjustment of the propeller governor for the left engine results in a similar control of the propeller pitch motor control circuit for the left engine (not shown) to cause the left engine tachometers to indicate an engine speed of 2400 revolutions per minute.

The interaction between the RPM, propeller pitch, brake horse-power, thrust horse-power, true air speed and propeller slip ratio motor control circuits will take place in the manner previously described.

When the pilot ascertains from the altimeter reading that the simulated flight has reached the desired altitude he will, in order to level off for efficient cruising, reduce the engine speeds to about 1900 revolutions per minute at manifold pressures of 27 inches of mercury. To simulate these conditions the pilot first reduces the throttle openings. The reduction of the throttle opening for the right engine reduces the potential of phase pl applied as previously described under the control of the throttle controlled rheostats 106 and 101 to the signal input conductor 401 of the manifold pressure motor control Icircuit whereupon the motor 354 thereof 

